Sally wants to buy some groceries. She wants to buy 2 kg of potatoes and 1 kg of onions. 1 kg of onions cost $5 but the paper that shows price of potatoes got lost. However, Sally remembers that few weeks ago she bought 3 kg of potatoes for $12. How much did Sally spent buying groceries?
Part 1: First we need to find how much 1 kg of potatoes cost. 3*x = 12 x = 4 1 kg of potatoes cost $4
Part 2: Now we need to find how much did she spent. M = 4*2 + 1*5 = $13.